Guide ray or beacon course method



Patented May 21, 1940 PATENT OFFICE GUIDE RAY OR BEACON COURSE METHOD Giinthcr Ulbricht, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a corporation of Germany Application November 11, 1937, Serial No. 173,978 In Germany October 21, 1936 4 Claims.

In blind landing the cue for the proper direction (line) of approach to the airport or landing field is imparted to the pilot by way of the radio beacon course which is produced by shifting the 5 radiation characteristic or diagram of. ultra-short wave dipoles by the rhythmic opening and closing of two reflector dipoles disposed symmetrically to the main dipole as well known in the prior art.

In other words, the pilot is in constant com-.

munication with ground through the blindlanding beacon.

Now, according to this invention this communication channel or connection is to be utilized for the purpose of imparting to the pilot such news as generally relates to the landing. According to prior practice this signalling was effected through a long-wave transmitter and receiver. The beacon transmitter which heretofore was modulated with a wave of 1150 cps, is with this end in view modulated by a frequency which lies outside the audible range or band, say, 20 kcs. This frequency in turn is modulated with a voice frequency; in other words, with a frequency ranging between 200 and 1600 cps. The total spectrum will appear in the receiver as being subject to rhythmic intensity modulations, in accordance with the beam identification or coding, for instance, by the so-called ET method. But if. the pilot is in the proper radio course bearing, then the keying modulation will be inaudible; in other words, the average level of the voice frequency is constant.

In the receiver apparatus, by the use of suitable filters, separation of the voice frequencies and the beam frequency is effected. Following the filter for the voice frequency, the voice modulation will be perceivable by ear.

The guide-ray frequency (20 kcs.), as heretofore, may be utilized for an optical course indication. However, in order that the pilot may also receive a similar indication by acoustic means, the guide-ray frequency, which is inherently inaudible, is to be stepped down by a frequency divider circuit scheme to an audible note such as 1000 cps. In addition, ways and means are provided so that this note may be put in the receiver telephones by the agency of a switch or a blending means. In this way, also, the signal strength is adjustable.

Fig. 1 shows the fundamental key diagram of the transmitter, while Figure 2 shows the fundamental key diagram of the receiver. The transmitter shown in Figure 1 comprises microphone circuit a, microphone amplifier b, the generator for the guide-ray frequency (course frequency) of 20 kcs. c, and the radio frequency generator at. The incoming signal is amplified in the radio frequency amplifier e and is thereupon rectified in the detector The guide-ray frequency of 20 kcs is filtered out by course filter g and imparted to the usual indicator instrument g; and in addition, this inaudible or supersonic modulation frequency is rectified in the rectifier h in order to obtain the voice frequency which is fed to the primary winding of a transformer m. By the aid of potentiometer I, included in the plate circuit of the rectifier, it is possible to regulate the volume of the voice frequencies. The guide-ray frequency of 20 kcs. is also fed through a frequency divider arrangement 76 in order to step the same down to an audible tone, say, of 1000 cps. This audible frequency is also fed to the transformer m. A headset is connected with the secondary of the transformer. By the aid of the potentiometer 2 it is feasible to regulate the volume of this signal also.

Assuming that, initially, the pilot is flying outside the range of the course bearing, he will manipulate things so that, in addition to the voice frequencies, he will read in his phones, also, the sound due to the guide-ray, and he will make an attempt to steer his craft so as to fly inside the equi-signal course. After he has located the latter, he may disconnect the guide-ray note in n order that the voice modulation may come in without any disturbance. By reading the visual or optical instrument he is able to check up on whether he keeps inside the equi-signal course as he proceeds. Since, also, the voice is carried by the course signal he will also be aware if, and when, he deviates from the proper course. Moreover, for a further check-up he is able at any time to switch in for a short while the guide-ray note and adjust the same to such intensity that the voice will be drowned out.

I claim:

1. A method of signalling for blind landing of aircraft along a radio beacon course comprising the steps of so modulating a beacon signal at a supersonic frequency for course indication that the course indication along a predetermined path is an uninterrupted wave and modulating the said supersonic frequency with voice frequencies for vocal landing instructions to the pilot of said aircraft.

2. A method of signalling for blind landing of aircraft along a radio beacon course comprising the steps of so modulating a beacon signal at a supersonic frequency for course indication that the course indication along a predetermined path is an uninterrupted Wave, modulating said supersonic frequency with voice frequencies, receiving the beacon signal, rectifying the beacon signal to obtain the supersonic wave, applying said wave to a course indicator for the course indication, demodulating said supersonic frequency, and receiving the voice frequencies.

3. A method of signalling for blind landing of aircraft along a radio beacon course comprising the steps of so modulating a beacon signal at a supersonic frequency for course indication that the course indication along a predetermined path is an uninterrupted Wave, and modulating said supersonic frequency with voice frequencies for vocal landing instructions to the pilot of said aircraft whereby any interruption of the supersonic frequency causes a corresponding interruption of the voice frequencies.

4. A method of signalling for blind landing of aircraft along a radio beacon course comprising the steps of so modulating a beacon signal at a supersonic frequency for course indication that the course indication along a predetermined path is an uninterrupted wave, modulating said supersonic frequency with voice frequencies, re-

ceiving the beacon signal, rectifying the beacon GiiNTI-IER. ULBRICHT. 

